Charge steering of laser plasma accelerated fast ions in a liquid spray - Creation of MeV negative ion and neutral atom beams

The scenario of electron capture and loss has been recently proposed for the formation of negative ion and neutral atom beams with up to MeV kinetic energy [S. Ter-Avetisyan, Appl. Phys. Lett. 99, 051501 (2011)]. Validation of these processes and of their generic nature is here provided in experiments where the ion source and the interaction medium have been spatially separated. Fast positive ions accelerated from a laser plasma source are sent through a cold spray where their charge is changed. Such formed neutral atom or negative ion has nearly the same momentum as the original positive ion. Experiments are released for protons, carbon, and oxygen ions and corresponding beams of negative ions and neutral atoms have been obtained. The electron capture and loss phenomenon is confirmed to be the origin of the negative ion and neutral atom beams. The equilibrium ratios of different charge components and cross sections have been measured. Our method is general and allows the creation of beams of neutral atoms and negative ions for different species which inherit the characteristics of the positive ion source.

How much multiuser diversity is required over large-scale fading?

In multiuser diversity systems, the impact of large-scale fading on the total system performance such as link quality and system power has not been widely addressed. Considering large-scale fading, we propose an adaptive multiuser scheduling to minimize the total system power while reducing the effect of large-scale fading on the system bit error rate. The number of active users is adapted to every shadow variation, which varies slower than small-scale fading. We consider the two widely used multiuser systems (i.e., delay-tolerant, and delay-sensitive multiuser systems). Closed-form expressions for the bit error rate are derived. The selection procedure for the minimum number of users is introduced for guaranteed performance of the above multiuser systems. The impact of adaptive multiuser diversity gain on the system power and bit error rate is illustrated over large-scale fading channels by numerical results.

Mitigating Cross-Network Interference in Cognitive Spectrum Sharing with Opportunistic Relaying

We examine the impact of primary and secondary interference on opportunistic relaying in cognitive spectrum sharing networks. In particular, new closed-form exact and asymptotic expressions for the outage probability of cognitive opportunistic relaying are derived over Rayleigh and Nakagami-m fading channels. Our analysis presents revealing insights into the diversity and array gains, diversity-multiplexing tradeoff, impact of primary transceivers' positions, and the optimal position of relays. We highlight that cognitive opportunistic relaying achieves the full diversity gain which is a product of the number of relays and the minimum Nakagami-m fading parameter in the secondary network. Furthermore, we confirm that the diversity gain reduces to zero when the peak interference constraint in the secondary network is proportional to the interference power from the primary network.

Ergodic Capacity of Cognitive TAS/GSC Relaying in Nakagami-m Fading Channels

We examine the impact of transmit antenna selection with receive generalized selection combining (TAS/GSC) for cognitive decode-and-forward (DF) relaying in Nakagami-m fading channels. We select a single transmit antenna at the secondary transmitter which maximizes the receive signal-to-noise ratio (SNR) and combine a subset of receive antennas with the largest SNRs at the secondary receiver. In an effort to assess the performance, we first derive the probability density function and cumulative distribution function of the end-to-end SNR using the moment generating function. We then derive new exact closed-form expression for the ergodic capacity. More importantly, by deriving the asymptotic expression for the high SNR approximation of the ergodic capacity, we gather deep insights into the high SNR slope and the power offset. Our results show that the high SNR slope is 1/2 under the proportional interference power constraint. Under the fixed interference power constraint, the high SNR slope is zero.

The influence of market deregulation on fast food consumption and body mass index:A cross-national time series analysis

Objective
To investigate the effect of fast food consumption on mean population body mass index (BMI) and explore the possible influence of market deregulation on fast food consumption and BMI.

Methods
The within-country association between fast food consumption and BMI in 25 high-income member countries of the Organisation for Economic Co-operation and Development between 1999 and 2008 was explored through multivariate panel regression models, after adjustment for per capita gross domestic product, urbanization, trade openness, lifestyle indicators and other covariates. The possible mediating effect of annual per capita intake of soft drinks, animal fats and total calories on the association between fast food consumption and BMI was also analysed. Two-stage least squares regression models were conducted, using economic freedom as an instrumental variable, to study the causal effect of fast food consumption on BMI.

Findings
After adjustment for covariates, each 1-unit increase in annual fast food transactions per capita was associated with an increase of 0.033 kg/m2 in age-standardized BMI (95% confidence interval, CI: 0.013–0.052). Only the intake of soft drinks – not animal fat or total calories – mediated the observed association (β: 0.030; 95% CI: 0.010–0.050). Economic freedom was an independent predictor of fast food consumption (β: 0.27; 95% CI: 0.16–0.37). When economic freedom was used as an instrumental variable, the association between fast food and BMI weakened but remained significant (β: 0.023; 95% CI: 0.001–0.045).

Conclusion
Fast food consumption is an independent predictor of mean BMI in high-income countries. Market deregulation policies may contribute to the obesity epidemic by facilitating the spread of fast food.

Effects of buried high-Z layers on fast electron propagation

By extending a prior model [A. R. Bell, J.R. Davies, S. M. Guerin, Phys. Rev. E 58, 2471 (1998)], the magnetic field generated during the transport of a fast electron beam driven by an ultraintense laser in a solid target is derived analytically and applied to estimate the effect of such field on fast electron propagation through a buried high-Z layer in a lower-Z target. It is found that the effect gets weaker with the increase of the depth of the buried layer, the divergence of the fast electrons, and the laser intensity, indicating that magnetic field effects on the fast electron divergence as measured from K-a X-ray emission may need to be considered for moderate laser intensities. On the basis of the calculations, some considerations are made on how one can mitigate the effect of the magnetic field generated at the interface.